In recent years, optical waveguides have been attracting attention as optical transmission media that meet the demand for increased capacity and speed of information processing in optical communication systems, computers, etc.
Quartz waveguides are representative optical waveguides, but have problems in that they require special production facilities, long production times, etc.
As substitutes for such quartz waveguides, organic polymer optical waveguides which are free from the above problems have been developed. Organic polymer optical waveguides are produced by forming a film of an optical waveguide-forming resin composition using a spin coater on a rigid substrate made of a rigid material such as a resin impregnated with a ceramic, glass, glass epoxy or like reinforcing material, and then curing the film.
When producing an organic polymer optical waveguide using such a resin composition, because of the difference in the coefficient of thermal expansion between the resin composition and the substrate, heat treatment causes cracks in the organic polymer optical waveguide, which has a high coefficient of thermal expansion, or peeling of the optical waveguide from the substrate, thereby producing transmission loss. JP 2002-277664 A discloses an optical waveguide-forming resin composition containing inorganic particles to reduce the thermal expansion of the composition.
However, optical waveguides formed using such a resin composition have insufficient mechanical strength since the inorganic particles have poor adhesion to the organic polymeric material. Further, the composition cannot be formed into a dry film and is thus limited in application. Furthermore, since the inorganic particles scatter light, the resin composition also has problems in that it cannot form a transparent optical waveguide and in that the organic polymeric material itself has insufficient heat resistance.